May be to much data not enough ram memory. Some of your stuff running in the background my be bottle necking your system. A lot of anti virus programs that are designed for newer computers that are installed on old computers, have way to much data being processed and it slows it way down while it's running tasks. You can try setting it on manual and only running updates when you want. Or there may be other open apps running in the background that are slowing it down.
Try resetting the network settings and closing out any apps that your not using or are running background tasks.